Mass Effect and branching storyline (at least for the end) is not seen as a shining example.

The Longest Journey is kind of old now, but has been known for a while as one of the best integrations of dialogue puzzles into adventure games. Or there are open-world games like Skyrim, but each individual quest within it is either linear or has 2 endings. I like interactive story games, but dang it's been a long time since I played one that had more than 2 endings... Even the time loop ones intend the player to see all the content in a more or less linear manner, that line just takes the player through the game's main event sequence 2 or 3 times. Which I can sympathize with, because it is kind of wasteful to develop content that some players will never see.

As a general piece of advice though, instead of the term "branching" like in your title, you might be better off thinking in terms of modular story, or a procedural interactive story and NPC system - the kind of thing that includes faction and individual reputation, mood gauges, key words, and item exchange.

branching storyline games are an evolution of basic single storyline based games. branching, then converging to a single outcome is more common than branching to multiple possible endings, as its less work.

the trend now is, as sunandshadow says, towards episodic storytelling in the context of a larger open world type setting. the player "encounters" succeeding "chapters" of the story as they move though, explore, and interact with the game world. such episodic storyline quests / campaigns can be branching, or non-branching.

unfortunately, meaningful choice is something that most consider to still be woefully lacking in most storyline based games. your actions have no impact on the world. save the world in skyrim, and they still treat you like just another adventurer. for most games, the limit is having player actions affect player relations with various factions.

OTOH, i'm playing Mad Max these days, and it has some of the elements you mention. multiple solutions to challenges. player actions affect the game world (relations, encounter chances, and availability of resources). but i don't really see any evidence of branching in the storyline. the main storyline quest series is pretty linear. side quests all appear to be single quests. no multiple questlines like skyrim.

the fact is that branching storylines can quickly grow exponentially in size as the number of branches increases, so they are much bigger investment in man-hours / days / weeks / months of work.

The Longest Journey is kind of old now, but has been known for a while as one of the best integrations of dialogue puzzles into adventure games. Or there are open-world games like Skyrim, but each individual quest within it is either linear or has 2 endings. I like interactive story games, but dang it's been a long time since I played one that had more than 2 endings... Even the time loop ones intend the player to see all the content in a more or less linear manner, that line just takes the player through the game's main event sequence 2 or 3 times. Which I can sympathize with, because it is kind of wasteful to develop content that some players will never see.

As a general piece of advice though, instead of the term "branching" like in your title, you might be better off thinking in terms of modular story, or a procedural interactive story and NPC system - the kind of thing that includes faction and individual reputation, mood gauges, key words, and item exchange.

I'll check out The Longest Journey, thanks.

About "key words, and item exchange", what do you mean?

And modular story?

Any examples ?

Key Words are ways for players to exchange information with NPCs; grammar is too hard for AI, and players don't want to be typing at AIs anyway, so instead you come up with a set of 10 or fewer key words for the whole game, and put that in your NPC template, and then you set each individual NPC to know about some of them and react to learning about others either through a global event or through 'conversation' with the player. The player may also enjoy the collecting aspect of discovering new key words as they explore the world. For example, the player may examine some graffiti and learn the key word "Denizen", presumably a graffiti artist or gang name. Then, each time the player talks to an NPC they see the list of key words that they have collected so far, color-coded for how that NPC will react to each of them. The categories would be: no reaction, already discussed, NPC has new info, and player is able to give info to the NPC. Digimon CyberSleuth has key words but it's a dumbed-down system because the game is aimed at a young audience. I'm sory, I can't recall a better example offhand, maybe someone else here can supply one.

Item exchange is when you can give or sell inventory items to NPCs and NPCs can give or sell inventory items to you, and then NPCs react appropriately to what they have received. In the Harvest Moon series, for example, the entire list of items in the game is part of the NPC template, and each NPC has settings for how much the like or dislike getting each item as a present. In other games like Skyrim and WoW, NPC merchants like it when you do business with them (raising your reputation with them) and if the merchant is aligned with an NPC faction they will offer the player a different attitude, different goods, and different prices, depending on the player's reputation with the faction and also the player's level.

Modular story is when you allow the player to make choices, the game reacts to those choices, but because the unit of story is more or less self-contained the game doesn't need to remember much about what the player decided. For example if the player chose a dialogue option that offended an NPC, that NPC's relationship with the NPC and/or mood will decrease, but the details of the player's choice don't matter beyond that, so the game doesn't need to remember them, and more importantly, doesn't need to figure out how to react to remembering all 20 or 30 dialogue choices the player has made so far. Whereas with a traditional branching story every choice is remembered and they accumulate into a mess unless there are only a few in the whole game. The Mass Effect series is an example where the designers got overwhelmed with the number of decisions made in the first two games, and made players mad when they decided to discard a bunch of the data about past decisions in the third game. (assuming I remember correctly how that went down...)

branching storyline games are an evolution of basic single storyline based games. branching, then converging to a single outcome is more common than branching to multiple possible endings, as its less work.

the trend now is, as sunandshadow says, towards episodic storytelling in the context of a larger open world type setting. the player "encounters" succeeding "chapters" of the story as they move though, explore, and interact with the game world. such episodic storyline quests / campaigns can be branching, or non-branching.

unfortunately, meaningful choice is something that most consider to still be woefully lacking in most storyline based games. your actions have no impact on the world. save the world in skyrim, and they still treat you like just another adventurer. for most games, the limit is having player actions affect player relations with various factions.

OTOH, i'm playing Mad Max these days, and it has some of the elements you mention. multiple solutions to challenges. player actions affect the game world (relations, encounter chances, and availability of resources). but i don't really see any evidence of branching in the storyline. the main storyline quest series is pretty linear. side quests all appear to be single quests. no multiple questlines like skyrim.

the fact is that branching storylines can quickly grow exponentially in size as the number of branches increases, so they are much bigger investment in man-hours / days / weeks / months of work.

The fact is, at the beginning my idea of this branching storylines thing came to my mind because i believed that "the more agency the player has , the better in any case".

But i was wrong.

Indeed i watched a video by Extra Credits:

where they explain that a lot of choice is not needed in every game and in every scenario within a game, it depends on the game and scenario.

There are cases where choice would give benefits to the gameplay experience, others where it can be useless , but still expensive to develop.

The question they say you have to ask yourself is "Does my game always give enough choice to make players believe their actions matter?", considering the type of game , the particular situations within the game.

The problem is answering this question, learning how to design/develop a game with the best possible agency/interactivity for a particular in-game situation , with practical examples.
If you can point me at some books or resources explaining that, i would appreciate.

I kind of disagree there. Making choices can matter to the player even if the choices themselves don't matter to the game at all - the choice of clothing, mount, which pet monsters to battle with, and all those other aesthetic choices are the most obvious example. But beyond that, I'd say the the key aspect of player choices that that the game reacts appropriately to them, which is a vital part of the game being an immersive virtual world.

For example, let's consider time loop games. In most cases the second play is extremely unsatisfying because the game totally fails to react to the fact that the player should remember which decisions went badly before (even if they didn't actually get to choose them the first time). The second play throughshould have new choice options because the player knows way more than they did the first time around; if the main character can't remember anything and the player can't guide them on a better path than before, that completely undercuts any time-loop related story as well as the player's agency.

learning how to design/develop a game with the best possible agency/interactivity for a particular in-game situation , with practical examples. If you can point me at some books or resources explaining that, i would appreciate.

learn by doing. go out and play some games!

that's the kind of question any hard core gamer worth their salt could answer in a heartbeat.

its a question that can only really be answered by experience and empirical evidence. there is no real underlying theory to study. in scientific and engineering terms, player agency is a "how-to" not a "why" science. so unless someone plays a ton of games then writes a book on what types of choices to present when (which is still just an opinion), you're out of luck.

You should play RPGs by Obsidian. ie, top to bottom, Tyranny, Fallout New Vegas and Pillars of Eternity. At least for my tastes, Obsidian does really well the whole branching storyline thing. Bethesda's Fallouts? (ie, 3 and 4) Not so much.

While Pillars of Eternity is a pretty long RPG, Tyranny is shorter but much more free in the choices department. Fallout New Vegas alone has tons of factions you can piss off or ally with. Good stuff. Much better done than Bioware 's "good/evil/sarcastic" or the "Yes/yes, but later" from Bethesda.